youtubebeat/vendor/github.com/antchfx/xpath/README.md

XPath

XPath is Go package provides selecting nodes from XML, HTML or other documents using XPath expression.

Implementation

• htmlquery - an XPath query package for HTML document

• xmlquery - an XPath query package for XML document.

• jsonquery - an XPath query package for JSON document

Supported Features

The basic XPath patterns.

The basic XPath patterns cover 90% of the cases that most stylesheets will need.

• node : Selects all child elements with nodeName of node.

• * : Selects all child elements.

• @attr : Selects the attribute attr.

• @* : Selects all attributes.

• node() : Matches an org.w3c.dom.Node.

• text() : Matches a org.w3c.dom.Text node.

• comment() : Matches a comment.

• . : Selects the current node.

• .. : Selects the parent of current node.

• / : Selects the document node.

• a[expr] : Select only those nodes matching a which also satisfy the expression expr.

• a[n] : Selects the nth matching node matching a When a filter's expression is a number, XPath selects based on position.

• a/b : For each node matching a, add the nodes matching b to the result.

• a//b : For each node matching a, add the descendant nodes matching b to the result.

• //b : Returns elements in the entire document matching b.

• a|b : All nodes matching a or b, union operation(not boolean or).

Node Axes

• child::* : The child axis selects children of the current node.

• descendant::* : The descendant axis selects descendants of the current node. It is equivalent to '//'.

• descendant-or-self::* : Selects descendants including the current node.

• attribute::* : Selects attributes of the current element. It is equivalent to @*

• following-sibling::* : Selects nodes after the current node.

• preceding-sibling::* : Selects nodes before the current node.

• following::* : Selects the first matching node following in document order, excluding descendants.

• preceding::* : Selects the first matching node preceding in document order, excluding ancestors.

• parent::* : Selects the parent if it matches. The '..' pattern from the core is equivalent to 'parent::node()'.

• ancestor::* : Selects matching ancestors.

• ancestor-or-self::* : Selects ancestors including the current node.

• self::* : Selects the current node. '.' is equivalent to 'self::node()'.

Expressions

The gxpath supported three types: number, boolean, string.

• path : Selects nodes based on the path.

• a = b : Standard comparisons.

  • a = b True if a equals b.
  • a != b True if a is not equal to b.
  • a < b True if a is less than b.
  • a <= b True if a is less than or equal to b.
  • a > b True if a is greater than b.
  • a >= b True if a is greater than or equal to b.

• a + b : Arithmetic expressions.

  • - a Unary minus
  • a + b Add
  • a - b Substract
  • a * b Multiply
  • a div b Divide
  • a mod b Floating point mod, like Java.

• a or b : Boolean or operation.

• a and b : Boolean and operation.

• (expr) : Parenthesized expressions.

• fun(arg1, ..., argn) : Function calls:

Function	Supported
boolean()	✓
ceiling()	✓
choose()	✗
concat()	✓
contains()	✓
count()	✓
current()	✗
document()	✗
element-available()	✗
ends-with()	✓
false()	✓
floor()	✓
format-number()	✗
function-available()	✗
generate-id()	✗
id()	✗
key()	✗
lang()	✗
last()	✓
local-name()	✓
name()	✓
namespace-uri()	✓
normalize-space()	✓
not()	✓
number()	✓
position()	✓
round()	✓
starts-with()	✓
string()	✓
string-length()	✓
substring()	✓
substring-after()	✓
substring-before()	✓
sum()	✓
system-property()	✗
translate()	✓
true()	✓
unparsed-entity-url()	✗